This invention relates to an improvement of a multi-pole armature winding of a polyphase dynamo-electric machine such as an induction motor.
In a prior art armature winding, where the number of slots q per pole per phase is larger than 1, the following relationship holds: EQU P=z/(m.times.q) . . . (1)
where P represents the number of poles, z the number of slots, and m the number of phases.
Accordingly, where the number of slots z is constant, in order to maximize the number of poles it is necessary to make minimum the product of the number of phases m and the number of slots q, per pole, per phase. Since the number of phases m is constant, it is possible to maximize the number of poles P by making 1 the number of slots q, per pole per phase. In this case, all magnetic poles formed by this coil are real poles and the number of coils per phase is equal to the number of poles P.
Some of the prior art armature windings were wound to change the connection so as to change the number of poles thus producing two speeds. In this case, the number of poles P becomes a maximum when the number of slots q, per pole per phase is selected to be equal to 0.5.
In a winding in which the number of slots q, per pole per phase is 0.5 where Q coils are connected to form poles of the same polarity there is a design wherein real poles formed by the coils and apparent or imaginary poles, also known as consequent poles, intermediate of the real poles alternate regularly so that where the number of coils Q per phase is equal to z/m and the number of poles is equal to twice of the number of coils Q per phase. FIG. 1 shows this coil arrangement in which Arabic numerals show slot numbers, letter a the upper coil of phase I, a' the lower coil of phase I, b and b' the upper and lower coils of phase II, and c and c' the upper and lower coils of phase III.
The voltage vectors of this winding have 120.degree. phase difference as shown in FIG. 2.
With the winding in which the real poles and the imaginary poles alternate regularly, the maximum number of poles is at most 2 times Q (in the example shown in FIG. 1, 24). For this reason, it has been desired to develop an improved armature winding that can increase the number of poles while maintaining the number of slots at a constant value.